An Etymological Dictionary of Astronomy and Astrophysics
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The speed an object must attain in order to free itself from the gravitational influence of an astronomical body. It is the minimum velocity for the object to enter a parabolic trajectory. The escape velocity is given by: V_e = (2GM/r)^1/2, where G is the → gravitational constant, M is the mass of the astronomical body, and r is its radius. The escape velocity of the Earth is about 11.2 km s^-1 that of the Moon is 2.4 km s^-1. The escape velocity from the Sun is about 618 km s^-1, and the solar escape velocity from Earth's orbit is about 42.1 km s^-1.

→ escape; → velocity.